1. Field of the Invention
This invention relates to drainage of fire hydrants and, more particularly, to an air valve assembly for use in a fire hydrant where the air valve assembly operates in cooperation with conventional drain valves to automatically drain excess water from the fire hydrant after the cap has been placed on the nozzle of the fire hydrant. This invention further relates to an air valve assembly and hydrant in combination and to a method of constructing a hydrant to drain automatically.
2. Description of the Prior Art
Fire hydrants should be drained after they are used to remove any excess water that is sitting in the barrel of the fire hydrant. As this task takes time, it is often overlooked by the user and the cap is replaced on the nozzle of the fire hydrant resulting in an air-tight seal so that any remaining water stays prematurely within the fire hydrant. As a result, any water left in the barrel stagnates resulting in possible contamination to the potable water supply. Remaining water can also result in damage to the hydrant if the water freezes thereby cracking the barrel and/or damaging other components. Municipalities incur significant costs to repair and maintain their fire hydrant systems.
Ellis is the owner of U.S. Pat. No. 3,980,097, which issued on Sep. 14, 1976. This patent relates to a fire hydrant of the “dry” barrel type having an improved means of draining the barrel after the hydrant has been used and the main hydrant valve closed. The hydrant is provided with a drain passageway from the interior of the barrel above the main hydrant valve to the exterior of the valve. A first valve means, which is automatically opened or closed by actuation of the main hydrant valve element, is arranged to close the drain passageway when the main hydrant valve element is open and to open the drain passageway when the main hydrant valve element is closed. A pressure responsive one-way check valve in series with the valve means in said drain passage is automatically actuated to open position by pressure of water when there is water in the hydrant barrel and the valve means in series therewith in the drain passageway is open. The one-way check valve automatically closes when the barrel is dry and prevents ingress of water and dirt, grit or other foreign matter from the exterior of each to the interior, thereby protecting the main hydrant valve and its associated operating mechanism.
Previous hydrants have drain valves near a base of the barrel that open when the hydrant is shut off to allow the barrel to drain. However, when the airtight caps on the nozzle are replaced before the barrel has drained, the water stops draining as no air can enter the barrel above the level of the water that remains in the barrel. The water remains trapped in the barrel even though the drain valves near the base of the barrel remain open. In cold climates, municipalities often have all hydrants inspected before the onset of freezing temperatures to ensure that the hydrants are properly drained. These inspections are extremely expensive. If a hydrant is not properly drained after use and the water within the hydrant freezes, the hydrant will be inoperable and unavailable for use in fighting a fire.
Thus an air valve assembly for a fire hydrant which allows residual water in the barrel of the fire hydrant to be drained away after the cap has been placed on the nozzle, thereby removing any risk to the potable water supply by draining away any stagnating water, as well as removing any risk of damage to the fire hydrant if water froze within the barrel while at the same time reducing the time a user would have to spend waiting for the water to drain is desirable.